Automatic telephone system



Dec-

W. T. POWELL 7 AUTOMATIC TELEPHONE SYSTEM 2 Sheets heat 1 Ori Filed Nov. 17 1920 Q Q I -4- w. T. POWELL AUTOMATIC TELEPHONE SYSTEM I Dec. 7

Original Filea'wov. 17, 1920 2 Sheets-Sheet. 2

Patented Dec. 7, 1926,

ENTTE ST DELAWARE.

Original appl ieetion llo iemli'ei This mle'ne mene'iiiee e m m eph e tems and t e bi z fif th 11We t 'O 1,-.,br9fld y fit i i P10371518 01 con jiti ig the .n nnhei qf c alls cl i 'e ctecl te a gi'oup f li'nes hieh fail because all of the nes-inn group. re busyi 1;; :1 HBI QtQfOLQ. so called gotg y cqnnectoi's h ve been ,us efm:eom e ns bmi st en t idl 1 .a p ura ity 9i ll f lines extending to the samepointahcl the sanie ,telephone number, The linesof a certein group, for.- ena nple, which my be,

trunklinesextending to a prine te biivnnch exchange, are t -er1ni natecl in sepa ate cbntact setsin the banks of ngponp at these rotary cgnnetgrsnnd a telephgne number is as signed in accordance With the fii'stcentact setin the ,g '0 1p. .l l lien the number is called the rotary connector taken for vuse il1,c0nneet,yvith the first cqntact set nd therefore withthe fi st trunk line in the "gronpg igf such tr mk line is iclle, but if the trunk line is busy the cennector will automatically operate-t0 test therest of the tlfLlIllC lines in order; an the first pnefonncl iclle. h I I V I V flhe nboye'clescribes the ;usnaln1ethocl of handling calls A to 'pIlVfl lI6-.br a li1( l'l exchange trunk lines, and this is perhaps the preferred method in most csses g,v It may hztp'peil, howeven thstrthere are only one 911 two groups Cf such trunk lines and the I pnoyisiqn of 3 special gmnp pf connecte 's I for handling the traflic will he ii cliplyexpeiis ii e. V Other situations also rn gly g ise Wherethe new method pt handling 1 these calls, which, will n wib-e p in ican be u t9 d, advantage, In the presentinvention rclingry standard connectors which have 'nowau tomatic rotary lnovernent are used, nnd e nly one. set f contacts is assigned to an entii'e giioi'ip fper1 aps fi ve or six trunk lines. This contact set is not nnlt iplecl hetweenthe several cohnectonsfof the group, biitsepai'gite lineslegid aw 'iy freifn-the cOntzict setin each connector to finder switches, onevgf ii hichis assbciatecl iirith each bf the privite exchange trunk lines the-group, these sep ri'atewlines, QT, 1in1eci gits ef which thei e ivill qhx idusly be as ndziny thei'e are cenneetei" .swmehss; ere, multiple-cl in the hanks-Ol en the finclei sfii itehes. .When the shiimbef ssigned t0 the fireiip efprivate 32w ie-@ 15 3; 1924. Serial No. 703,894.

cl will connect with meme gPi'eT-en-T ewes,

"0' -AS'SIGLIdR BY-MESN E- Assmm 0F 'GEICAG'O', ILLINOIS, A CORPORATION 0F AUTOMATIC TELEEITOITE ST sTEM.

I mm

blitlnich ,ex'eh t'rnhli lines cli'llea the ce'nn'ectbi 'tziken fo r use l ontact set in itso 'n bank net, xjw hrenponthe fin ef ilclle trunk finder will .lb'cate the link circuit donning fjom th'e' pzirtlblllait ceiniiectqi'" inse, end will eo jne' tit through to the trunk line zisspeiat'e'cl i3, tl'ie' -fi n 'cl'en siiiit h i 1 l. this applic z tibn is alldiylsioi i-dlt" ily ni' iemm N -fizemi filed, Ne ve b61317, 1920, phiin's jn the-present a pp ll catidn ai'fe l11n 1teq:l; ";0 bl 1e feet Line Of registering lost. calls, eth f tnres h'elnlg claimed. in the it men pn'fil ab There zi'fe othef e"a ;tii1 es' als Wh 11 together tli'e us ual nigh;- tch' associated with the abdi e will be f illy desci'ihecl iiiafi qwi h fefe'rencf t6 the aeomp r win s; diagrams ,pfthe @6 11 "nt in use,- While Fig. 3. is esqhenjatic diagram bf the trunking arrangem nt. 7 w i.

Ref ih l fi e; o; ile- .3 Zt i k f e arrangement will first briefly explained,

as this' will Tender it, ieli' td u ncle vstgincl sm matlic .v .l y' f the circuits shows insgwpk f'efnnthe trunking between ldc'a'l siib'sc'ribersili an 'ziutp'infatle eneh ajn cl Nals'o the; trnnkijn arrange ents by h ch su h 6 1 1 u Q lfi lli ces's tq afgreujp bit-nil; lines extendinga p ivnte bi-afnh gxcbqi ge, Considering. the means which the l'oc'a'l snb'serib'ers' mfe interconnected, let us assnnie thzit t h'e sill)- s ciibei sit siih station A e siies" to obtain confnectipn, with g snbscfibe'r ttsilhststion A. Th'e 'co'n'neetig'n may be established by means 9f .the vjinclivilcliifzil line switch 0 a; first select'pr, sw tch s has the first selectnr E, and cjinnecter si'X 1 t ch siicl1 as the connecto i H. This, is the jc'qfclina 'y percentzig tn'inking ystem inmmm i se l 1 C ei eif is' 116W. th me by w ch cennections aye enfte lecl to the privat branch ei switch F which is 'as'spc'iated 5 line In the connectbr signed lqwfih briv e;1 ene. xc i, trunk lines; the refm'ainlng contzict sets" beell and ep ilieatien filedji'lbril connef r H, H, nd H ll connect with the. v

e isstz rtedencl which Figs, 1.511(12 af-f'e ei ricuit ing assigned to ordinary subscribers lines in the usual manner. Thus in the drawing, which shows only part of one level in each of the connector switches, the second, third and fourth contact sets in the connectors are multipled together and are assigned to subscribers lines, while the first contact set 1s not multipled but separate conductors extend from this contact set in each connector switch to multiply connected contact sets in the banks of the finder switches F and F With this explanation the process of extending a connection from substation A to the private branch exchange trunk line X for example will readily be understood, at least so far as the general method is concerned. The connection is extended by means of the individual line switch C, a selector switch such as the selector E, a connector switch such as the connector H, and the finder switch F. If the trunk line X had happened to be busy when the call was made the finder switch F would have operated to extend the connection to the trunk line Y, or some other finder switch not shown would have been operated to extend the connection to one ofthe other trunk lines. 7

Having explained the trunking arrangement adopted, the apparatus shownin the circuit diagrams may now be briefly described. The substation A, Fig. 1, is an ordinary automatic telephone substation having the usual talkinginstrinnentalities and a calling device S for controlling the automatic switches. The line conductors terminate at the exchange in the individual line switch C, which may be of any well known type, such for example as the rotary type of line switch indicated in Fig. 3. In

developing the present invention, however, the well known plunger type of line switches have been used, such as are shown and described in the U. S. patent to Newforth, No. 13,901, reissued April 13th, 1915, and accordingly this is the type whichlias been shown'in the'drawing.

The first selector E and the connector H are of the usual Strowger vertical and rotary type so far as their mechanical construction is concerned and any well known type of two wire circuits may be used. In view of the fact that these circuits are well known. only the circuit of the connector switch H is shown infull, and reference is made to the previously mentioned patent to Newforth for the circuits of the selector switch.

The connector H and the other connectors of the same group have access in common to a plurality of subscribers lines, and each of theseconnectors also has access to a separate line or trunk circuit which is used for extending calls to the private branch exchange trunk lines. Only one of these separate or individual lines is shown in the drawing, this being the line associated with the connector H and comprising conductors 86, 87, and 88. Each of these lines is provided with a pair of relays, and the relays associated with the line shown are indicated by the reference character T. 1 These relays control the starting. of the finder switches of which, as before stat-ed, there will be as many as there are private branch exchange trunk lines. The finder switch F associated with trunk line X is a simple rotary switch of the type in which the Wipers'have no normal position and move in a forward direction only. ,The operation of the circuits will be fully described later on.

The line switch C is individual to the trunk line X, and is 'provided'for the purose of handling connections from the private branch exchange to the main exchange. This line switch is similar to the line switch G associated with the substation A, and it may have access to the same group'of first selector switches.

The reference character M indicates a meter which is common to all the finder switches associated with the group of trunk lines under consideration. Its function is to register the number of times the private branch exchange is called when all the trunk lines are busy.

Having briefiy explained the purpose of the invention and the apparatus involved in carrying it out, the operation of this equipment may now be explainedmore in detail. For this purpose it will be assumed that the subscriber at substation A desires to obtain connection with a subscriber in the private branch exchange served by the trunk line X and other associated trunk lines.

When the calling subscriber at substation A removes his receiver to initiate the call, an energizing circuit is completed over the line conductors ll'and 12 for the line relay 14 of the line switch 0. Upon energizing, the line relay lit closes a circuit'for the pull in winding 18 which, upon energizing, operates both the plunger arm 15 and the cut-off armature 16; the former throughthe medium of its plunger (not shown) forces the bank springs 30453, inclusive, into engagement, respectively, with the contacts 34:37, inclusive, and the latter disconnects the line conductors 11 and 12, from the line relay lt and from ground, respectively. By the engagement of bank springs 80 and 83 with contacts 34 and 37, respectively, the line conductors l1 and 12 are extendedto the line relay (not shown but corresponding to relay-51 of connector switch H) of the lector E.

The selector E now. places ground on re lease trunk conductor 41 in the well known manner to close a holding circuit for the line switch C extending from grounded re lease trunk conductor 41 through the bank contact 35, bank spring 31, and through the Ill) 104. The operation now depends upon whether the test wiper116 is standing upon ungrounde'd contact 113 or upon some other contact which will, of course, be grounded. e will assume the latter, in which case relay 102 will be short circuited and motor magnet 104 will operate as a buzzer to advance the switch wipers step by step in search of the calling line. When wiper 116 arrives at ungrounded contact 113 the relay 102, being no longer short, circuited, will energize over its above traced circuit. The relay 102 is of such high resistance that the motor magnet 104 will not energize in series with it. Upon energizing, relay 102 extends the trunkline X by way of respective working contacts of armatures 122 and 125 and said armatures, wipers 115 and 117, contacts 112 and 114, and conductors 86 and 88 to contacts 83 and 85 in the bankof connector H; disconnects the starting conductor 130, at its armature 123, from relay 103 and connects it to the conductor 135 leading to the next switch; and shifts the test wiper 116 at armature 124 to the grounded release trunk conductor 131, thus closing a circuit for relay 100 which extends by way of test contact 113, through armature 110fandits working contact, and relay 100 to battery. Relay 100, upon energizing, opens the circuit to relay 101 at armature 109, removes ground from the starting wire 130 at its armature 108, and locks itself to ground from the grounded conductor 87 at armature 105. Armature 105 also grounds the test contact 113, and does so before the slow acting relay 108 of thefinder F has had time to fall back; thus ,it is seen that the established connection of the finder switch is held up.

Returning to the connector we find that the passage of the side switch wipers 90'and 91 to third position and the closing of contacts at armatures 97 and 98 by the deenergization of the slow acting relay 57, finally completes the connection between the calling line and the called trunk line. The passage of the side switch wiper 63 into third position completes the circuit for the ringing relay 56. This circuit extends from ground G? through interrupter I, relay 56, resting contactof armature 92 and said armature, and through side switch wiper 63 to battery. The relay 56, upon energizing, disconnects the calling line from the called trunk, and connects ringing current generator K with the latter through, the 'armatures 93 and 94 and their working con tacts, armature-s 97 and 98 and their resting contacts, wipers 80 and 82, and over previously traced circuits to trunk line X and thence to a ring down drop or some other visual or audible signal in series with a condenser at the switchboard of the private branch exchange. Since the circuit of the ringing relay 56 includes the interrupter I, said relay is energized only intermittently. When the operator plugs in to answer the call she closes a conductive bridge across the line, and as soon thereafter asthe ringing relay 56 deenergizes, a circuit is completed over the heavy talking conductors for the double wound back bridge relay 50. Relay .50 is accordingly energized and closes the circuit of ring cut-off relay 55 The relay 55, upon energizing, opens the circuit of the ringing relay 56 at the armature 92 and closes a locking circuit for itself, independent oirelay 50, at its armature 99, so as not to fall back and start the ringing again in case the operator at the branch exchange should disconnect before the calling party replaces his receiver. The operation of relay 50'serves also to reverse the direction of the,

which operates to restore the connector H to normal position in the usual manner. Relay 52 also disconnects groundfrom the release trunk conductor 58, thereby breaking the holding circuit of the selector E and the line switch C and these two switches are restored to normal also. WVhen the con nector H releases ground is removed from conductor 87, thus breaking the holding circuit extending forward to the relay combination T and finder switch F. Relay 100 accordingly deenergizes, likewise relay 102 of finder switch F, and the cut-cit winding 132 of the line switch C.

. In the foregoing it hasbeen assumed that the first trunk line leading to the private branch exchange is idle when the call is made. In case the first trunk line is busy, the starting wire 130 will have been extended to the next finder switch, and the connection will be completed in the same manner but over a different trunk line. In case all trunk lines are busy the connector H will not complete the connection but will give the calling subscriber a busy signal and also will operate the meter M, which registers the number of times that the private branch exchange is called when all the trunks are busy. In orderto explain this we will as sume that the subscriber atsubstation A makes the same call as before, but that all the trunk lines leading to the private branch through coii'ductcif t6 'test' cqntaet' 84 in the bfcoiiiiectqr "Now when 00.1;- n'eptcr resphhs'e t6 the List digit l'bf the 'cd-Ied' num-b'ener'l retz tie sfits wipers 80,: 81, zmd 82 intb engigrriehfwith contacts through side-"switchmprm wh ch is 111* second p6siti0n,')' hqriii ally closed" contacts cont'relled' by "arin'zitfire" 89, reI'a'y" normally closed contacts controlled 'by airmat 'ure""64;'eiid thriigh'prii iteihegnet 651 battery; Armature "63 closes this circuit he'- fc're' "it; disciiii'cts'grciiiid from private n zi'gnet GSfiiid, 'therefcre; magnet 65 does not deenei giz'e zindfdhes "hbitipe'riiiit the side switchwi 'ders t6"p ass"1"nte third pcsiticn,"

thus pi-eventing thEOniictidh 'fiom being relay '54, fi'po'n eiiergiiiiig ever" the." circuit gr'opn'di G hy Wiy cuffhermal sprin 39. and its working 'cont'zict, zind tir'm'atu'rje 89' stire the cpe'r'atich' o'f"the metf'M; sooii falls back opens" the "ci'rciiifl le w ing the meter M iree'tb redster ino'ther' call should it' c oiiie in while; a;1]," the truiiks are still busy: Intidditiontb the cp'eratiqii's described relay 54: also tion f em he, s5..,, through the rm'atiir'e completes a comn'ec s g r glling machine 38 and its WOI'KlIlg contact, and through side switch Wiper 91 to the hailing-"hue to' etify the calling subchange is busy. After hawiiig"called-"emf hiie, the calling siib'scriber ca iises the release been gamed;

As explainedbefiore the line switch 0' is provided "handling, calls from the pri- Vilte exchange ttit-h'mziui ex'cha'rige thetrunk' hne X 'b'ei 'ng What is knovv n} as 'a fishinga, coiine ctiii" of-"this'kihd is according'td'wefi iih'de'rstood peaches, antrsin'ce ithas" nothing" art enlar' tb do i with the release triihk" e11;1 iiego1-"131' is grdiindd "dur' mg abraiich to" ma'ineiichh'ge c'a'li, relay 102' or the fihdf switch 'F- dhesiiot frilly 6per'zite 'its several afniiitursQdhe 'tq 'a r'nechziii iczillockiiig device cn't'roi ied by th-e hii relay 103, s1i"ch"is 'discl'bsed in thei'pat'eiit t0 Lamb; No] 1,193,160, aiii'd the Wipers olf -the stifitchiare not ccnfiected ii'p'. Armature 123',

however; is' 's'b'eidj listed that wider-"these ci'i ciiihsthces it enga es it's fr'iificorit zlct ih order to prqperly extend the starting 'ivir-e' t6 the iiez it fin'ders'wifch.

"Haiti rig descii-bed ihy inventipn, What I coiisider to bene'ivmid desireft'c have'prd tectedby LettersPateiit itiifiiihepciiited out in the gl p 'pended defies: I

' is 'cl giimed is} 1.111" a' telephbiie system, an automatic switch, at groufi bf" trunk'ilihes" accessible to s'ziid switch; aihetercciiihicri idem-gro p of trurrk l l es, megins inch d ng a relay 111- dlvrdual-te each trunk for pre arin Ia meter conifer ci rcitii t iyhen 5111 slid .t'nirik "line's fire busy, and means ln'said switch for ciosljiig ive to the busy henchmen of an em trii'ril':

linesiqr preparing a circuit forsqid rel iij; 211id ihezi'iis 'fc'ii' closiiig'j'said'; circuit 'in case said' switch operated iii zinf'zittenipt tbf ccil'nect with 'ric' "cf said. trunk lilies While switches interve fiih between "the hanks (if said sWitcheshQndsaid truiik IihesQ m ans for operating an idle iii tbiiitic switch and an idlScbfi-dary swltch to extend a'conne etiqn to 'aii'idle' truhlrliheg'zifiiieter in said secondary; switch; aiid hiealis "controlled said mitbmatie' ew i't'ch *roi-"oprati rig "said meter in case it is attempted to extend a connection to one of said trunk lines while they are all busy.

4. In a telephone system, automatic switches, trunk lines accessible to said switches, secondary switches intervening between the banks of said switches and said trunk lines, means for operating an idle automatic switch and an idle secondary switch to extend a connection to an idle trunk line, means for preventing the operation of any of said secondary switches incase it is attempted to extend a connection to one of said trunk lines While they are all busy, a meter, and means for operating said meter to register the uncompleted connection.

5. In a telephone system, a line, a group of trunk lines, finder switches individual to said trunk lines and having access to said line at one end thereof, means for connecting with said line at the other end, means responsive to such connection for starting an idle finder, means for preventing the starting of any of said finders in case the said trunk lines are all busy, a'meter, and means for operating said meter whenever said line is connected with and a finder fails to start.

6. In a telephone system, a line, a group of trunk lines, finder switches individual to said trunk lines and having access to said line at one end thereof, means for connecting with said line at the other end, means responsive to such connection for starting an idle finder, a meter, and means for operating said meter whenever said line is connected with at a time when all said finders are busy. I

7. In a telephone system, a group of lines, automatic switches for extending connections to said lines, a second and smaller group of lines, secondary switches 'for extending. connected lines of the first group to idle lines of the second group, means for rendering the remaining lines of the first group busy as soon as all the linesof the second group are in use, and means for registering the number of attempted connections which fail because all said lines are busy.

8. In a telephone system, a group of lines, automatic switches for extending connections to said lines, a second and smaller group of lines, secondaryswitches for extending connected lines of the first group to idle lines of the second group, means for making the remaining lines of the first group busy as soon as all the lines of the second v group are in use, a meter, and means for operating said meter whenever a line of the first group is connected with while busy.

'9. In a telephone system, a line, means for making said line busy, a connector switch, means for directively operating said switch in accordance with the last two digitsin a telephone number to connect with said line, means in said connector for testing said line, a meter, and means for operating said meter. responsive to establishing a connection between the wipers of said switch and said line but eifective only in case said line is tested and is found busy.

10. In a telephone system, an automatic switch having means for establishing telephone connections, a line accessible to said switch, means for making said line busy, means for operating said switch to connect with and to engage only said line, a meter, and means effective only in case said line is busy for operating said meter responsive to 1 the establishment of said connection.

11. In a telephone system, an automatic switch, a plurality of lines accessible from one set of bank contactsin said switch, means for making saidelines busy, means for advancing the wipers of said switch to said set of bank contacts and for stopping said wipers in engagement with said contacts, a meter, and means effective only in case all said lines are busy for operating said meter when said wipers are stopped on said contacts.

12. In a telephone system, an automatic switch, a. plurality of lines accessible from a set of bank contacts in said switch, means for making said lines busy, means for advancing the wipers of said switch to said set of bank contacts and for stopping said wipers in engagement with said contacts, a meter, and a circuit for controlling said meter completed by said switch through a wiper thereof and one of said contacts in case all said lines are busy.

13. In a telephone system, aline, an automatic switch, a set of contacts individual to said line in the bank of said switch and including test and talking conductors, means for placing a busy potential on one of said contacts, substation controlled means for, opcrating said switch .to cause its wipersto-engage and stop on said set of contacts, a meter, and means responsive to said busy poten-. tial for operating said meter in case the switch wipers are stopped on said set of contacts while the busy potential is on.

14. In a telephone system, a group of subscribers lines, agroup of trunk lines, indi vidual line switches for extending calling subscribers lines to idle trunk lines, a relay, circuit connections for operating said relay only in case a line should attempt to call while all of said trunks are busy, and a meter controlled by said relay.

In witness whereof,I hereunto subscribe my name this 19th day of March, A.'D., 1924:.

WINFRED T. POWELL. 

